Accurate measurement of weight and height

In particular, height measurement is often done too quickly and/or without good technique. Weight should be measured with minimal clothing on a well-calibrated scale with the subject in a neutral hydration state. The tendency is to diminish, at least subconsciously, the significance of these measurements, especially height, because of the focus on percent body fat. However, an accurate measurement of both height and weight are essential when calculating body mass index (BMI) and even body surface area (BSA), if desired.

Calculation of body mass index

Body mass index (BMI) is underutilized in body composition analysis and counseling. Although it is limited to the relationship between height and weight, BMI is generally considered to be a more sensitive indication of appropriate body weight. BMI carries a fairly high correlation with cardiovascular disease risk, with well-established norms.3 BMI is calculated as: wt(kg) ÷ [ht(m) x ht(m)]. For example, an individual who is 72 inches tall (1.83 meters) and weighs 183 pounds (83 kg) has a BMI of 24.8, which is considered to carry a low to very low disease risk (Table 1).

A measurement of waist-to-hip ratio

The waist-to-hip ratio has become increasingly recognized as a good indicator of cardiovascular disease risk.3 Although the two measurements can be done quickly and with minimal client discomfort, it is absolutely essential that the technician adhere to simple, yet strict testing procedures.

The waist measurement is done at the narrowest circumference, while the hip measurement is done at the greatest circumference (with feet together). A high-quality spring tension tape measure should be used, with a taut (any slack will overestimate the reading) position that avoids compression of the skin (underestimate of measurement will result). The tape measure must be held parallel to the floor and read straight on (at eye level).

Selecting a method

Selecting and administering reliable, cost-effective and clinically feasible methods represents the most difficult decision regarding body composition analysis. There are numerous body fat measurement methodologies on the market including, but not limited to, circumference measurements, skin-folds (of which there are many different anatomical measurement sites and regression formulas), hydrostatic weighing (the longstanding so-called "gold standard" estimate), bioelectrical impedance, near infrared analysis, and total body potassium determination. In addition, a new method based upon the principle of air displacement (plethysmographic measurement) has recently emerged.2 Your choice as a technician, clinical program director, physician or other health and fitness professional must take into account the reliability (including standard error of measurement), cost and clinical feasibility of the various techniques. Let us define the above terms.

Reliability. Reliability refers to the degree to which test results can be reproduced by one or more technicians at one point in time, as well as changes, if any, over a period of time. A reliable method will allow for an acceptable longitudinal tracking capability for individuals as they adopt changes in their lifestyle. The ultimate goal is the ability to reasonably measure relative changes in body composition. For example, if you estimate someone's body fat to be 20 percent at a scale weight of 180 pounds in June, your method should be able to estimate this person's body fat at several percentage points lower if they come back in October after four months of quality cardiovascular endurance and resistance training, a much-improved diet, and weighing 165 pounds.

Reliability does not mean validity, which strictly speaking is impossible to achieve with body fat analysis because it is always an indirect estimate in living human beings. Your goal is to choose a method that is not only reliable over time, but that also has a relatively small standard error of measurement (SEM). Every method of assessing body fat has a standard error, which is best expressed as the range of actual values in which a given measurement most likely falls.

An SEM of plus or minus 5 percent means that for the vast majority (95 percent) of individuals assessed, actual body fat, which cannot be directly measured, is somewhere within 5 percent of the measured, estimated reading. For example, a person measured at 20 percent body fat has a 95 percent probability of actually being 19 percent to 21 percent body fat. Note that the SEM refers to 5 percent of the measured value, and not to 5 percent body fat (5 percent of 20 percent = 1 percent).

It should now be evident how important it is to choose a method with an established low SEM. The larger the SEM, the less useful your initial body fat results become for lifestyle modification counseling and/or competitive athletic training guidelines. A large SEM also severely compromises your ability to reliably track estimated changes in actual body composition over time. When using a method with a relatively high SEM, it is not uncommon for someone to actually be estimated as fatter even though they have actually become leaner. And, of course, the opposite situation is just as likely to occur.

Cost. The cost of body composition analysis ranges from under $100 for some of the basic skinfold calipers to upwards of $30,000 for the plethysmographic technology. Cost is important in deciding which method to select for your program. Determine what choices you have within your allocated budget, then compare the various financially feasible methods using the reliability and clinical feasibility criteria. The least expensive option may not be the best method for your clinical needs.

Clinical feasibility. This term refers to the collective logistics of implementing a given body composition methodology. This includes, but is not limited to: 1) staff qualifications/experience and availability for longitudinal tracking (same technician testing client for each assessment if possible); 2) space availability; 3) degree of client/patient compliance required; 4) potential for client/patient discomfort or embarrassment; 5) time requirement/restraints (including a thorough counseling session).

Consider the typical profile of your clientele so that you choose a methodology that makes the most sense for the majority of the people you test. For example, you may desire to install a hydrostatic tank and have the budgetary approval for one. But if your typical client is non-athletic and/or apprehensive of either water, disrobing or both, and is interested mostly in "just getting an idea of how fat I am," installing a hydrostatic tank would not be cost-effective.

Should you consider selecting two or more methods of body composition? You certainly can consider this option if it meets your budgetary criterion. Be very careful not to create an adverse clinical situation, however in terms of time restraints and, even more importantly, in potentially selecting two methods that can yield significantly different results (i.e., large intrasubject variance). If this happens, your counseling session can become a very difficult attempt to explain the discrepancy in results. This situation tends to discredit the clinical facility. It also impairs your discussion of lifestyle modifications and goals with your client.

One suggestion for selecting a method(s) is to create a scoresheet grid and grade each of your potential choices on the criteria listed above, as well as on other criteria you deem important. The various criteria should be weighed according to the anticipated relevance each has to your program (Table 2).

Counseling session protocol

The counseling session is extremely important. Allow for adequate time to cover every relevant issue, including any questions and concerns of your client. The underlying theme of the counseling session should emphasize the importance of achieving and maintaining a healthy body composition that helps reduce the risk of developing serious chronic illness such as cardiovascular disease, hypertension, diabetes and certain cancers. Beyond the objective of an acceptable healthy body composition, you can certainly discuss your client's fitness goals.

The following sample counseling session protocol is recommended.

* A concise statement regarding the fact that body composition is an indirect estimate of body fat. Briefly explain, in lay terms, the meaning and significance of reliability, SEM and longitudinal tracking.

* A concise, yet thorough explanation of BMI and waist-to-hip ratio, including a discussion of norms and correlation to disease risk (Table 1) .

* A thorough explanation of your client's estimated percent body fat and lean body mass (LBM). This should include the use of reasonable age and sex-specific norms for percent body fat. There are literally dozens of norms from which to choose. Your goal and responsibility is to select norms you feel comfortable with, not only professionally, but also in terms of how closely they represent your typical clientele. You may even decide to have two or more sets of norms to use, depending on the individual client you are testing.

Explanation of norms is a critical juncture in the counseling process. Many people will come into your facility with a "magical" percent body fat number in their head. If their estimated percent body fat exceeds this number, they have a tendency to block out the remainder of the counseling session.

If you sense this happening, redirect your client's focus on the issues related to lifestyle modification and longitudinal tracking. From experience, this seems to be best accomplished for most people by adopting a firm yet very understanding tone. Your client needs to realize that there are several important principles that still need to be discussed and that need to be applied in their effort to improve their body composition.

* An effective description of the physiologically significant interrelationship between BMI, waist-to-hip ratio and percent body fat. Although many clients will possess a similar profile on all three measurements, some people have a disparity, in any or all possible combinations, between these various body composition indices. An example is a female who is estimated to be 38 percent body fat (high), but who has a waist-to-hip ratio of 0.85 (moderate risk). This person certainly should be encouraged to reduce her body fat. However, her risk for cardiovascular disease is not as high as it would be for another woman with similar percent body fat but proportionately more upper body girth. Another example is a male with a BMI of 36 (high), but an estimated 10 percent body fat; in other words, an individual with considerable lean body mass relative to his height. This person obviously does not need to lower his BMI in an ill-guided attempt to get into the average range.

* Recommendations for other relevant assessment(s) and professional services that will facilitate the client's effort to improve their body composition, as well as overall health and fitness. Recognize the capabilities and limitations of you and your staff. Even if the person conducting the counseling session is educated and trained (licensed, certified, registered, etc.) as a fitness technician and/or exercise specialist, instruct this person to refer your client to the appropriate professional (staff member or perhaps independent contractor) for further counseling on an individual topic. For example a registered dietitian or nutritionist can provide dietary analysis and counseling, and a highly qualified personal trainer can assist a competitive, athletic client.

Conversely, if the person who initially meets with your client possesses strong dietary and nutritional credentials but has a limited exercise science background, you have a professional obligation to arrange for your client to meet with someone qualified to develop, discuss, implement and track a comprehensive exercise program.

Certain clients may benefit from referral to a psychologist, social worker or other qualified professional who can address the psychosocial aspects of lifestyle modification, especially as it applies to body composition, body image and/or emotional eating disorders.

The most common auxiliary assessments sometimes warranted are dietary analysis, basal metabolic rate (BMR) testing and various levels of blood draw analysis (e.g., blood chemistry, complete blood count, coronary risk panel, thyroid panel). Your ultimate professional responsibility is to not merely assess body composition, but to also address the comprehensive needs of our clients. We know that a very high percentage of people who are concerned or struggling with their body composition are at significantly increased risk for many serious physical and emotional conditions. Fair or poor body composition is usually a symptom of several related underlying problems that need to be addressed in a comprehensive and professional manner by your entire staff.

* An individualized longitudinal tracking and goal-setting schedule, including discussion of your client's complete exercise and dietary modification program. These goals need to be physiologically sound as well as reasonably flexible, especially in terms of potential modifications at a later point. In fact, your clients' goals should be reviewed, discussed and updated as necessary at each follow-up session. In general, a rigid set of goals, even if objectively feasible, tends to place most people at a greater risk of failure in their attempt to achieve and maintain an improvement in their body composition.

It is also important to emphasize to your client the concept of associating success in their program with gaining improvement in their body composition and overall well-being, rather than focusing on losing body weight or body fat! The majority of people who come to you will be fixated, to varying degrees, on losing weight. One of your greatest challenges will be to help your client change their perspective from hinging their entire emotional well-being on every pound to recognizing how good they can feel with positive lifestyle changes that will not only help them improve their body composition over the long-term, but also help them gain much better lifelong health.

Your norm chart may say that a 40-year-old male should ideally be between 12 and 15 percent body fat. However, you need to set realistic, attainable goals for each client; for example, perhaps approximately (remember, you are estimating) 20 to 24 percent body fat after six months of lifestyle modification for your 40-year-old male client who is currently estimated to be 28 percent body fat. These goals can then be reviewed and adjusted at the six-month follow-up period to reflect your client's current body composition and lifestyle status.

The first follow-up tracking should be scheduled at least three, but no more than six, months after the initial assessment. If the follow-up assessment is done sooner, you risk under- or overestimating your client's improvement, because any actual change in percent body fat in that time frame could easily be masked within the SEM of most methods (approximately 2 to 3 percent body fat). An initial follow-up assessment scheduled too soon also tends to place unnecessary, counterproductive pressure on clients.

Conversely, when a follow-up assessment, especially the initial one, is scheduled more than six months later, you run a much greater risk of losing track of your client. Clients are much more likely to stray from their healthy lifestyle in this scenario, and you increase the chances of losing a valuable client in your program.

Guide your clients through the goal-setting process, but make sure that they actively contribute to establishing their goals and the means by which they will attempt to accomplish them. This is their life, and they need to feel empowered to actively improve their health and fitness. They also need to assume the responsibility for taking charge of their lifestyle and following through on reasonable, physiologically sound commitments to improving their body composition and, therefore, their overall health profile.

It is also important to carefully use the calculation of target body weight (TBW) to body fat, and always with qualification and clarifications. The most common formula involves dividing the person's current LBM by the desired (target) percent lean body mass in order to derive a target body weight that, in theory, will result in this individual profiling at the desired percentages of body fat and LBM:

TBW = Current LBM (pounds) ÷ target percent LBM.

Example: current weight = 200 pounds, current percent body fat = 25 percent.

Therefore, current percentage LBM = 75 percent and current LBM = 150 pounds; target LBM = 80 percent (20 percent body fat);

TBW = 150÷.80 = 187.5 pounds.

In other words, at 187.5 pounds, a person would be estimated to be 20 percent fat, with 80 percent LBM of 150 pounds. However, you cannot merely calculate target/ideal body weight and routinely tell your clients that "this is the weight that will put you at "X" percent body fat." Sure, the math is clean and it would be nice to just plug in the numbers, hand them to your client and say "get to this weight and you are all set," but there's more to it.

One of the most important physiological realities of body composition modification -- improvement -- is that reduction in percent of body fat does not necessarily mathematically correspond (correlate) exactly with the change (up or down) in scale weight for any given individual. Yes, you should definitely emphasize the desired goal of reducing storage body fat and maintaining lean mass. But you also need to specifically mention that the calculation of a target scale weight/percent body fat assumes no change in lean body mass.

Most individuals who do not engage in a moderate-to-high intensity aerobic and/or resistance training exercise program tend to lose at least some lean tissue during the course of reducing their body fat (fortunately, the decline in lean tissue is typically modest, especially when the individual follows a nutritionally sound dietary plan and consistently engages in a regular cardiovascular endurance program). Then there are other individuals who will actually be increasing their lean body mass, sometimes significantly, as a result of fairly intense resistance training, concurrent with their reduction in storage body fat.

Consequently, the initial target scale weight/percent body fat calculation may have, for example, predicted 15 percent body fat at 200 pounds for a male who is currently 212.5 pounds and estimated to be 20 percent body fat/80 percent lean body mass and, therefore, 170 pounds of lean body mass (LBM). However, at his initial follow-up assessment four months later, he weighs in at 200 pounds but is estimated to be 18 percent body fat and, therefore, only 82 percent lean body mass or 164 pounds of LBM. What you need to do in this situation is determine whether this discrepancy is due mostly to your client's exercise and dietary habits, inadequate adherence to your facility's clinical assessment protocol (therefore reducing the method's reliability/increasing its SEM), or a combination of the two. This will enable you to best address any needed modifications in either your client's program, your body composition assessment program, or both.

Discuss with your client the importance of reducing scale weight at a maximum long-term rate of one to two pounds per week. Make sure that they understand the importance of correct scale weight tracking -- weighing themselves once per week and every week under equivalent conditions (e.g., day of week, time of day, little or no clothing, similar hydration state) on the same well-calibrated scale every time.

As obvious as it should be to health and fitness professionals, you need to reinforce the fact that short-term (i.e., day-to-day or even hour-to-hour) fluctuations in scale weight are physiologically a result of fluid changes in the body and psychologically are to be avoided (by not constantly stepping on one or more scales). It is also imperative that you persuade your client to accept the physiological reality that the week-by-week rate of weight loss will vary and that they need to maintain their long-term commitment to lifestyle modifications that facilitate both body composition improvement and an enhanced level of health and well-being.

Another essential component of your goal-setting discussion is to take into account as much relevant information about them as possible, especially in terms of their overall health profile. Generally speaking, the greater their overall risk profile is for serious disease, the more concerned you want them to feel about improving their body composition, even if it is only estimated to be moderately elevated. In doing this, you want to avoid verbage or tone that could be construed as intimidating scare tactics. For example, "lose the fat or die soon." You need to strike a delicate balance between expressing the importance of reducing their body fat via healthful living versus sounding like an alarmist.

Be sure to provide educational handouts related, but not limited to: 1) nutritional guidelines, 2) exercise program guidelines and precautions and 3) meal planning and/or recipe information.

As helpful as educational material can be for your clients, it is the quality of your personal attention and professional guidance that is easily the most important aspect of your program for the vast majority of individuals. Highly technical and professional printouts and handouts are fine, provided they are presented and explained by qualified and caring health and fitness professionals.

Accordingly, you will want to go well beyond the data by learning about your client as a person. As in any counseling session, you need to be a very good listener. Pay special attention to what makes your client tick and what turns them off. They objectively may need to engage in aerobic endurance training six to eight hours per week and circuit weight training two to three days per week in order to make the best possible health and fitness improvements.

However, if you can facilitate their change from lifelong couch potato to three one-half hour walks per week and three to four days per week of calisthenics, they will be able to improve their health infinitely more than rejecting the former, "better" exercise program. Obviously, the same principle applies to dietary modifications. Ultimately, the effectiveness of your body composition assessment program will be determined primarily by how successful your clientele becomes in modifying and maintaining a healthy lifestyle, of which an improved body composition is an integral component.

REFERENCES

1. Dempster, P., & S. Aitkens. A new air displacement method for the determination of human body composition. Medicine and Science in Sports and Exercise 27, 1692-1697, 1995.

2. Hoeger, W., & S. Hoeger. Principles and Labs for Physical Fitness and Wellness. Englewood, CO: Morton Publishing Co., 1994, pp. 61-63.

3. Stensland, S.H., & S. Margolis. Simplifying the calculation of body mass index for quick reference. Journal of the American Dietetic Association 90, 856, 1990.